In this study, a novel acyl chloride monomer trimellitic anhydride chloride (TAC) with an anhydride group was blended with trimesoyl chloride (TMC) as organic phase monomers to fabricate high-flux nanofiltration membranes. Due to the reaction activity differences of organic phase monomers (TMC and TAC) with piperazine, the chemical compositions and structures of polyamide active layer could be tailored through varying the TAC content. It was found that the participation of TAC could yield a looser polyamide separation layer on the polysulfone support membrane, along with an increased surface roughness, hydrophilicity, pore size and negative charge density. As a result, the resultant membrane exhibited excellent water-salt separation. When the TAC concentration was increased to 0.04 wt%, the optimized membrane exhibited a high pure water permeability (PWP) of 13.2 Lm(-2)h(-1) bar(-1), up to 2-fold, in comparison with the pristine membrane, whereas the salt rejections of Na2SO4, MgSO4 and NaCl were 97.6%, 92.7%, and 34.0%, respectively. This work provided a novel and facile strategy to develop high-flux NF membrane.